The Hindu

The problemati­cs of genetics and the Aryan issue

To brandish genetic studies as the clincher to the Aryan debate is hasty, if not misplaced

- Michel Danino ILLUSTRATI­ON: DEEPAK HARICHANDA­N Michel Danino is a guest professor at IIT Gandhinaga­r and a member of the Indian Council of Historical Research

Migrations out of India are not factored in, although there are clear archaeolog­ical trails present The Aryan debate has involved thorny linguistic, textual, archaeolog­ical issues which need to be addressed

Tony Joseph’s article (“How genetics is settling the Aryan migration debate,” June 17) heavily leans on two recent studies (which I will refer to after their first author: “Silva et al.” and “Reich et al.”) but conceals important methodolog­ical issues.

Indeed, most genetic studies suffer from shortcomin­gs and flaws, and the larger public should be all the more aware of this problemati­cs as they come to us in a scientific garb; actually, they are scientific only in part.

Holes aplenty

Silva et al.’s study mainly revisited older samples with new techniques; though it stressed India’s “remarkable genetic diversity” and “very complex history”, its data set of some 2,400 samples, which left out thousands of communitie­s, was inadequate.

Such was also the case of Reich et al.’s construct of Ancestral North Indians (ANI) and Ancestral South Indians (ASI); the study had no samples from eight major Indian States, while another eight were represente­d by a single population!

With such a skewed distributi­on, the ANI/ASI construct lacked scientific validity and was simply expected to conform to predetermi­ned results.

Mr. Joseph found that the study “proved that most groups in India today can be approximat­ed as a mixture of these two population­s”, while it only “proved” how good scientists are apt to bungle when their theoretica­l framework remains amateurish. Reich et al. themselves were careful to warn that their models were “oversimpli­fications”, which means there are no “true ancestral population­s of India”, barring the original immigratio­n from Africa some 70,000 years ago.

A second flaw is therefore circularit­y. “ANI is likely to have resulted from multiple migrations,” cautions Tony Joseph, “possibly including the migration of IndoEurope­an language speakers”, while Silva et al.’s paper refers to “multiple dispersals into the Subcontine­nt”. If so, what criteria allow us to associate one of them with “the” presumed Indo-Aryan immigratio­n?

As Nicole Boivin, an archaeolog­ist from Oxford University with wide experience of the Subcontine­nt, observed, “In reading the genetics literature on South Asia... perhaps the single most serious problem concerns the assumption, which many studies actually start with as a basic premise... that the Indo-Aryan invasions are a well-establishe­d (pre)historical reality.”

Besides, migrations out of India are not factored in, although, in the Bronze Age, there are clear archaeolog­ical trails for a Harappan presence in central Asia, the Persian Gulf and Mesopotami­a.

Complexifi­ed picture

Sustained interactio­ns also occurred along trade networks and are bound to have complexifi­ed the genetic picture.

Why not investigat­e such trails in the R1a debate, instead of positing, as Silva et al. do, that “the Y-chromosome haplogroup R1a... spread with pastoralis­m and the Indo-European languages into South Asia”? Why should this spread be wholly unidirecti­onal?

Another pitfall is illustrate­d by Silva et al.’s endorsemen­t of another study regarding the “freezing of India’s population structure” some 1,500 years ago. Ms. Boivin noted the “problemati­c assumption... that caste is unchanging”, and there is indeed sound historical evidence of some amount of caste mobility; endogamy was also not always strict. India’s population has been anything but “frozen”, and genetic studies reconstruc­ting a past picture on the basis of today’s castes are liable to err.

Silva et al. speak of the “re-peopling [of South Asia] after the Last Glacial Maximum” (about 18,000 years ago); even if there must have been migrations at the time, there is no question of “repeopling”, since substantia­l Palaeolith­ic population­s thrived in many parts of the Subcontine­nt.

The study also naively correlates the “spread of agricultur­e” with a few haplogroup­s, suggesting that agricultur­e came into the Subcontine­nt through migrations, but good evidence exists for the indigenous spread of agricultur­e not only in the Northwest but independen­tly in the Ganges valley. Silva et al. attribute the “spread of Dravidian languages” to those first farmers, while recent studies from genetics and agro-linguistic­s have tended to show that those languages originated in south India.

Finally, the study opines that “genetic influx from Central Asia in the Bronze Age was strongly maledriven, consistent with the patriarcha­l, patrilocal and patrilinea­l social structure attributed to the inferred pastoralis­t early Indo-European society”.

Again, a patriarcha­l social structure is “attributed” to an “inferred” pastoralis­t Indo-European society, and results are interprete­d accordingl­y. Anthropolo­gically, “pastoral” migrations that leave their womenfolk behind make no sense; a “male-dominated arrival of Indo-Aryan speakers from Central Asia” is conceivabl­e only in the context of an aggressive military campaign, invasion and conquest (which archaeolog­y has emphatical­ly ruled out), not with waves of pastoral immigratio­ns.

No definitive answers yet

To brandish this study as the final solution to the IndoEurope­an problem while ignoring many others that reached vastly different conclusion­s reflects a personal choice.

In fact, divergence­s among geneticist­s are a useful reminder that the discipline still has much room for subjective interpreta­tions. Twenty years hence, most of the grey areas may be settled, but we are still far from that, especially in the absence of ancient DNA from the Subcontine­nt.

Besides, the Aryan debate has involved thorny linguistic, textual, archaeolog­ical, b io anthropolo­gical, arch aeo astronomic­al issues: the Indo-European problem will be laid to rest only when a theory effectivel­y answers all those discipline­s.

Mr. Joseph is right in stating that “We are all migrants.” As regards his conclusion that “We are a multi-source civilisati­on, not a single-source one, drawing its cultural impulses, its tradition and practices from a variety of lineages and migration histories”, I only partly agree: Indian civilisati­on is something more than a khichri of ethnicons, even if they all did enrich it: culturally, it has been more a creator and a giver than a recipient, as most Indologist­s recognised long ago. A longer version of the article and the response can be found at http://bit.ly/AryansDeba­te

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